Not able to stand the noise of the stock cooling I tried to put a fairly big cheap (€10) socket 754 heatsink (92x92mm) on the card. I had to mill two bits out of the heatsink to make it fit, and a drill broke which is now permanently a part of the heatsink. Luckily I just had enough room for a second set of holes..
As you can see I sandwiched a temperature sensor between the backplate and the back of the pcb. The maximum temp with stock cooling was 63c. Now, with a 120mm Nexus at ~660 RPM 'sort of' blowing over the heatsink (non ducted / very inefficient) the maximum temperature is 43! This translated in additional overclocking from 350 to 395 (325 stock). I don't have to explain that a 660rpm Nexus is a lot better to listen to than a 5000rpm 40mm screamer.
The backplate is essential and makes for a tight fit without any sort of bending of the pcb.